Many medical procedures in use today require a relatively small sample of a body fluid, such as blood or interstitial fluid, in the range of less than 50 μL. It is more cost effective and less traumatic to the patient to obtain such a sample by lancing or piercing the skin at a selected location, such as the finger or forearm, to enable the collection of 1 or 2 drops of blood, than by using a phlebotomist to draw a tube of venous blood. With the advent of home use tests for the self monitoring of blood glucose, there is a requirement for a simple procedure which can be performed in any setting without a person needing the assistance of a professional.
Lancets in conventional use generally have a rigid body and a sterile needle which protrudes from one end. The lancet may be used to pierce the skin, thereby enabling the expression of a blood sample. When a capillary tube or test strip is placed adjacent the expressed blood, the fluid can be collected. By a capillary tube fluid is then transferred to a test device, such as a paper testing strip. Blood is most commonly taken from the fingertips, where the supply is generally more accessible. However, the nerve density in this region causes significant pain in many patients. Sampling of alternative sites, such as earlobes and limbs, is sometimes practiced to lessen the pain. However, these sites are also less likely to provide sufficient blood samples and can make blood transfer directly to test devices more difficult. Additionally, it is often difficult for a user to determine whether a sufficiently large drop of body fluid has been expressed at the incision point to provide a sufficient sample.
Prior methods of acquiring a blood sample have suffered from the need to use two components and the resulting time lapse between the lancing action and placement of the capillary tube adjacent the lanced location, potentially allowing contamination or not collecting the fluid expressed from the body. One prior method for addressing this concern was to create a larger opening and/or to force excess fluid from the body. While this assisted in ensuring an adequate fluid supply, it potentially created a large opening to be healed and could cause the patient additional pain. Moreover, use of this method requires precise steps where the lancet is removed and the capillary tube or test strip is then correctly aligned with the lanced location. It is important for correct collection that no gap or movement of the capillary tube relative to the lanced location occur during collection. There is a need for a system to assist in removal of the lancet and placement of the capillary member with a minimum of time and movement. Further, there is a need for a compact, simple system to obtain the desired sample size without the need for excess lancing of tissue, extra pain to the patient or expressing an excess volume of body fluid.
To reduce the anxiety of piercing the skin and the associated pain, many spring loaded devices have been developed. The following two patents are representative of the devices which were developed in the 1980's for use with home diagnostic test products.
U.S. Pat. No. 4,503,856, Cornell et al., describes a spring loaded lancet injector. The reusable device interfaces with a disposable lancet. The lancet holder may be latched in a retracted position. When the user contacts a release, a spring causes the lancet to pierce the skin at high speed and then retract. The speed is important to reduce the pain associated with the puncture.
Levin et al., U.S. Pat. No. 4,517,978 describes a blood sampling instrument. This device, which is also spring loaded, uses a standard disposable lancet. The design enables easy and accurate positioning against a fingertip so the impact site can be readily determined. After the lancet pierces the skin, a bounce back spring retracts the lancet to a safe position within the device.
In home settings it is often desirable to collect a sample in order to enable a user to perform a test at home such as glucose monitoring. Some blood glucose monitoring systems, for example, require that the blood sample be applied to a test device which is in contact with a test instrument. In such situations, bringing the finger to the test device poses some risk of contamination of the sample with a previous sample that may not have been properly cleaned from the device.
Glucose monitoring devices utilize blood samples in many ways, though the two most common methods are a paper strip and a capillary tube. Monitors that utilize a paper strip require the patient to pierce a finger or appropriate location, withdraw a small sample of blood from the piercing, such as by squeezing, and then place the paper strip over the blood sample and wait until the paper strip absorbs the blood. Monitors that utilize a capillary tube require the patient to follow the process described above, except that a paper strip is not utilized to collect the blood from the skin. Instead, a small capillary tube is placed over the sample until a sufficient amount of blood is withdrawn into the capillary tube, which is then tested.
In some instances patients are diabetic, that is they are unable to properly metabolize glucose. In order to regulate insulin levels within their bodies, individuals who are diabetic must inject themselves with an appropriate amount of insulin. To determine the proper amount of insulin, an individual first must test their blood glucose levels. Typically, a patient has to ‘prick’ a fingertip with a lancet to create an incision through which blood can be withdrawn and placed on a glucose monitoring strip which then reacts and changes colors indicating the glucose level.
Haynes U.S. Pat. No. 4,920,977 describes a blood collection assembly with a lancet and micro-collection tube. This device incorporates a lancet and collection container in a single device. The lancing and collection are two separate activities, but the device is a convenient single disposable unit for situations when sample collection prior to use is desirable. Similar devices are disclosed in Sarrine U.S. Pat. No. 4,360,016 and O'Brian U.S. Pat. No. 4,924,879.
Jordan et al., U.S. Pat. Nos. 4,850,973 and 4,858,607 disclose a combination device which may alternatively be used as a syringe-type injection device or a lancing device with disposable solid needle lancet, depending on its configuration.
Lange et al., U.S. Pat. No. 5,318,584 describes a blood lancet device for withdrawing blood for diagnostic purposes. This invention uses a rotary/sliding transmission system to reduce the pain of lancing. The puncture depth is easily and precisely adjustable by the user.
Suzuki et al., U.S. Pat. No. 5,368,047, Dombrowski U.S. Pat. No. 4,653,513 and Ishibashi et al., U.S. Pat. No. 5,320,607 each describe suction-type blood samplers. These devices develop suction between the lancing site and the end of the device with the lancet holding mechanism withdrawing after piercing the skin. A flexible gasket around the end of the device helps seal the device end around the puncture site until an adequate sample is withdrawn from the puncture site or the user pulls the device away.
Garcia et al., U.S. Pat. No. 4,637,403 discloses a combination lancing and blood collection device which uses a capillary action passage to conduct body fluid to a separate test strip in the form of a micro-porous membrane. It is necessary to achieve a precise positioning of the upper end of the capillary passage with respect to the membrane in order to ensure that the body fluid from the passage is transferred to the membrane. If an appreciable gap exists therebetween, no transfer may occur. Also, the diameter of the capillary passage is relatively small, so the width of a sample transferred to the membrane may be too small to be measured by on-site measuring devices such as an optical measuring system or an electrochemical meter.
Single use devices have also been developed for single use tests, i.e. home cholesterol testing, and for institutional use, to eliminate the risk of cross-patient contamination with multi-patient use. Crosman et al., U.S. Pat. No. 4,869,249, and Swierczek U.S. Pat. No. 5,402,798, describe disposable, single use lancing devices.
The disclosures of the above patents are incorporated herein by reference.
An object of the present invention is to provide a disposable lancet unit that may be deployed easily and without causing undue pain.
Another object of the present invention is to provide a one-step system for sampling a body fluid for testing.
Another object of the present invention is to provide an apparatus that withdraws a blood sample and provides an individual with a blood glucose level reading.
A further object of the present invention is to provide an apparatus that does not require the user to perform multiple steps in order to produce a blood glucose level reading.
A further object of the present invention is to provide a lancet unit having capillary functions.
Further objects, features and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.